Optical fiber pressure sensors are needed for measurement of pressure in extreme high temperature, high pressure and corrosive environments such as oil well downholes, jet engines, or power generation equipment. Also, pressure sensors for these locations must be very small since space is limited. These requirements impose severe constraints on the sensor design and material composition. Also, since temperature can fluctuate in extreme environments, the pressure sensor for these extreme environments will ideally have negligible sensitivity to temperature.
Optical fiber pressure sensors typically have a Fabry Perot etalon cavity optically coupled to the fiber. The etalon is constructed so that applied force or hydrostatic pressure causes the etalon cavity length to change. The etalon cavity length is remotely monitored optically. For example, the reflectivity of the etalon at a specific wavelength or group of wavelengths can be monitored. In this way, pressure is measured optically.
Conventional fiber optic pressure sensor designs are typically not suitable for applications in extreme environments. The presence of metals in a sensor, for example, precludes use at high temperature and in corrosive environments. Also, thermal expansion mismatch between different materials can cause changes in temperature to appear as changes in pressure.
It would be an advance in the art to provide an optical fiber pressure sensor that can be used at high temperatures and in corrosive environments. It would be particularly beneficial for the pressure sensor to be chemically inert, very small, insensitive to temperature changes, easily manufacturable and inexpensive.